插补法CAI研究

数字程序控制计算机辅助教学是将计算机技术用于数字程序控制的教学过程，它帮助学生学习并模拟教学实验．本文介绍了数字程序控制中直线插补和圆孤插补的ＣＡＩ实现方法．     

Efficient parallel algorithms for numerical simulation

COUPL+ is a programming environment for applications using unstructured and hybrid grids for numerical simulations. It automates parallelization by handling the partitioning of data and dependent data and maintaining halo interfaces and copy coherency. We explore some algorithms behind this package. A multi-level partitioning method is described which is effective in the presence of skewed data, solving the multi-set median-finding problem. Partitioning elements over a set of pre-partitioned nodes is explored and a novel method is suggested for reducing communication in the resulting distribution.     

Interpolation for gain-scheduled control with guarantees

Here, a methodology is presented which considers the interpolation of linear time-invariant (LTI) controllers designed for different operating points of a nonlinear system in order to produce a gain-scheduled controller. Guarantees of closed-loop quadratic stability and performance at intermediate interpolation points are presented in terms of a set of linear matrix inequalities (LMIs). The proposed interpolation scheme can be applied in cases where the system must remain at the operating points most of the time and the transitions from one point to another rarely occur, e.g., chemical processes, satellites.     

插值算法的研究

主要研究应用于图像放大技术领域的处理算法,常用的图像放大技术即为插值算法,主要插值处理方法有最邻近插值算法、双线性插值法、双三次插值。实验仿真结果表明最邻近算法处理后的图像效果较差,双线性算法处理后图像质量较高。而双三次插值算法处理后的图像质量最高,但运行时间较长。     

手持式PDF417条码识读器算法改进

研究了对发生斜切变形的PDF417图像识别问题。主要采用控制栅格插值法纠正斜切变形。此方法用在手持式条码识读器上,可以提高使用上的方便性。     

Exact and fast numerical algorithms for the stochastic wave equation

On the basis of integral representations we propose fast numerical methods to solve the Cauchy problem for the stochastic wave equation without boundaries and with Dirichlet boundary conditions. The algorithms are exact in a probabilistic sense.     

Quantifying residual numerical diffusion in flux-corrected transport algorithms

Residual diffusion in fluid-dynamics calculations results from the finite order of approximation in the underlying linear algorithm, including the effect of smoothing sometimes added for numerical reasons, and, in the case of monotonicity-preserving algorithms such as flux-corrected transport (FCT), the nonlinear action of the flux limiter on steep profiles. Some widely used FCT algorithms contain a multiplicative constant that reduces the antidiffusion coefficient by 0.01%–0.1%. Replacing this constant with a smoothly varying function of velocity which equals unity when the Courant number vanishes causes the linear diffusion to go to zero when the flow velocity does. The use of a velocity-dependent antidiffusion coefficient minimizes numerical smearing of discontinuities and associated effects in the neighboring flow. Computational examples are presented. The residual diffusion for nonzero flow speeds is nonlinear and problem dependent. A method is presented for calibrating it in any given code in the context of a particular problem, and is applied to the FCT algorithms described here.     

分段抛物插值结点的选择

本文在分析了常用分段抛物插值结点选择方法的基础上,指出所存在的问题及其对计算结果的影响,最后给出了正确的选择方法。     

台达运动控制型PLC应用技术

本文介绍台达运动控制型PLC的应用技术。重点描述了台达DVP20PM运动控制型PLC的硬件和软件结构以及运动控制编程，并介绍在其应用中的方法及特点。     

A high quality interpolation method for colocated polyhedral/polygonal control volume methods

A high quality and efficient interpolation method for polyhedral/polygonal control volume simulation data is presented. The proposed method utilizes a non-ambiguous and efficient mesh decomposition technique. A pseudo-Laplacian is used to solve an optimization problem to approximate the variation between discrete data points in a linear fashion. The interpolation method guarantees continuous interpolation data throughout the control volume mesh topology and faithfully reproduces the input control volume data. The interpolation connectivity is structured to mimic the interpolation methods utilized by the control volume discretization. The method only requires the geometry of the input data to perform interpolations. This allows key interpolation data to be calculated once and stored for efficient interpolations. The benefits of the proposed algorithm are highlighted by an interpolation test case which demonstrates the benefits of the current method compared to a popular interpolation method currently used in industry. Since the proposed method is designed to augment an existing mesh data structure it can be used to update existing control volume software.     

Estimation of valve stiction in control loops using separable least-squares and global search algorithms

This contribution presents a new procedure for quantifying valve stiction in control loops based on global optimisation. Measurements of the controlled variable (PV) and controller output (OP) are used to estimate the parameters of a Hammerstein system, consisting of a connection of a two-parameter stiction model and a linear low-order process model. As the objective function is non-smooth, gradient-free optimisation algorithms, i.e., pattern search (PS) methods or genetic algorithms (GA), are used for fixing the global minimum of the parameters of the stiction model, subordinated with a least-squares estimator for identifying the linear model parameters. Some approaches for selecting the model structure of the linear model part are discussed. Results show that this novel optimisation-based technique recovers accurate and reliable estimates of the stiction model parameters, dead-band plus stick band (S) and slip jump (J), from normal (closed-loop) operating data for self-regulating and integrating processes. The robustness of the proposed approach was proven considering a range of test conditions including different process types, controller settings and measurement noise. Numerous simulation and industrial case studies are described to demonstrate the applicability of the presented techniques for different loops and for different amounts of stiction.     

Assessment of numerical optimization algorithms for the development of molecular models

In the pursuit to study the parameterization problem of molecular models with a broad perspective, this paper is focused on an isolated aspect: It is investigated, by which algorithms parameters can be best optimized simultaneously to different types of target data (experimental or theoretical) over a range of temperatures with the lowest number of iteration steps. As an example, nitrogen is regarded, where the intermolecular interactions are well described by the quadrupolar two-center Lennard-Jones model that has four state-independent parameters. The target data comprise experimental values for saturated liquid density, enthalpy of vaporization, and vapor pressure. For the purpose of testing algorithms, molecular simulations are entirely replaced by fit functions of vapor-liquid equilibrium (VLE) properties from the literature to assess efficiently the diverse numerical optimization algorithms investigated, being state-of-the-art gradient-based methods with very good convergency qualities. Additionally, artificial noise was superimposed onto the VLE fit results to evaluate the numerical optimization algorithms so that the calculation of molecular simulation data was mimicked. Large differences in the behavior of the individual optimization algorithms are found and some are identified to be capable to handle noisy function values.     

插值方法对GIS土壤养分插值结果的影响

精准农业技术的应用越来越受到大家的关注,通过对一个地块土壤养分进行详细栅格采样化验分析,利用反距离法和克里格(Kriging)两种不同计算机插值方法对土壤中各种营养元素进行了分析研究。在采样栅格大小不同的条件下,随机选择5个采样点插值,分析对比了5个采样点在不同栅格采样条件下利用两种插值方法的插值结果。通过插值计算得到土壤中全氮、速效氮和速效磷在采样栅格较小的情况下,由于反距离法考虑的周围点数较多,插值点处的插值误差要较克里格插值总体上来讲误差小,而随着采样栅格距离的加大,克里格插值的误差要小于反距离法插值的误差。     

Stochastic algorithms for robustness of control performances

In recent years, there has been a growing interest in developing statistical learning methods to provide approximate solutions to “difficult” control problems. In particular, randomized algorithms have become a very popular tool used for stability and performance analysis as well as for design of control systems. However, as randomized algorithms provide an efficient solution procedure to the “intractable” problems, stochastic methods bring closer to understanding the properties of the real systems. The topic of this paper is the use of stochastic methods in order to solve the problem of control robustness: the case of parametric stochastic uncertainty is considered. Necessary concepts regarding stochastic control theory and stochastic differential equations are introduced. Then a convergence analysis is provided by means of the Chernoff bounds, which guarantees robustness in mean and in probability. As an illustration, the robustness of control performances of example control systems is computed.     

Testing the performance of some nonparametric pattern recognition algorithms in realistic cases

The success obtained by Statistical Pattern Recognition in many disciplines is certainly related to the quality and availability of many data, normally distributed. However, in other disciplines, the data sets consist of few measurements, often binned, correlated, and not normally distributed. Usually, we do not even know which features have an influence on the process. The main goal of this paper is to evaluate the performance of some nonparametric Pattern Recognition algorithms when applied to such data. Finally we show the results of the application of the four nonparametric statistical pattern recognition techniques to real volcanological data.     

医学图像插值算法的研究

在医学图像的显示、处理和分析中,常需要将图像进行插值处理。另外,图像插值也是三维重建中的一个重要步骤．且插值结果的好坏直接影响到重建工作的进行。文中在PC机上实现了最近邻插值、线性插值、Lagrange插值、匹配插值、基于形状的插值和小波插值等。插值试验结果表明,基于灰度插值方法的特点是计算简单,计算速度比较快。但在不同密度物质处存在边界模糊现象;基于对象插值方法的特点能够比灰度插值更为精确的轮廓边缘,但一次插值不能得到整个图像;基于小波插值方法能够克服以上两种插值方法的缺点,但这种方法的最大缺点是计算量太大,难以运用到实际中。     

数字式预见控制的计算机算法研究

分析了计算机实现数字式预见控制的主要问题,给出了一种Riccati方程式的数字解法,提出了用计算机实现数字式预见控制的可行性和算法。研究表明这种算法的精度较高,易于计算机实现。     

A numerical method for deadbeat control of generalized state-space systems

In this paper we give a new numerical method for constructing a rank m correction BF to an n × n matrix A, such that the generalized eigenvalues of λE−(A+BF) are all at λ = 0. In the control literature, this problem is known as ‘deadbeat control’ of a generalized state-space system Ex_i+1 = Ax_i + Bu_i, whereby the matrix F is the ‘feedback matrix’ to be constructed.     

Multidimensional Spline Interpolation: Theory and Applications

Computing numerical solutions of household’s optimization, one often faces the problem of interpolating functions. As linear interpolation is not very good in fitting functions, various alternatives like polynomial interpolation, Chebyshev polynomials or splines were introduced. Cubic splines are much more flexible than polynomials, since the former are only twice continuously differentiable on the interpolation interval. In this paper, we present a fast algorithm for cubic spline interpolation, which is based on the precondition of equidistant interpolation nodes. Our approach is faster and easier to implement than the often applied B-Spline approach. Furthermore, we will show how to loosen the precondition of equidistant points with strictly monotone, continuous one-to-one mappings. Finally, we present a straightforward generalization to multidimensional cubic spline interpolation.